Semiconductor device and test method thereof

ABSTRACT

A semiconductor device includes: a command control circuit for decoding a command signal to output a test signal and a normal control signal; a normal circuit for performing a predetermined operation in response to the normal control signal; and a test circuit for testing electrical characteristics of unit elements provided in the normal circuit in response to the test signal.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.11/647,147 filed on Dec. 29, 2006, now U.S. Pat. No. 7,564,254, whichclaims priority of Korean patent application number 10-2006-0083532filed on Aug. 31, 2006. The disclosure of each of the foregoingapplications is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device, and moreparticularly, to a test circuit for testing a semiconductor device.

DESCRIPTION OF RELATED ARTS

Generally, semiconductor devices are formed on silicon wafers. Severaltens to several hundreds of semiconductor devices are formed on onewafer. The semiconductor devices are tested for normal operation, andonly normal semiconductor devices are packaged and put into the market.

The semiconductor devices are tested at the wafer level in variousmethods. An electrical parameter test method is to test unit elements ofthe semiconductor device for the designed electric characteristics. Afunction test method is to test for the semiconductor device operationas designed. This method tests if an output signal of the semiconductordevice is normal with respect to an input signal.

In order to test the electrical parameters, a constant voltage isapplied to MOS transistors and resistors, which are unit elements of thesemiconductor device, and currents flowing through them are measured.However, it is almost impossible to apply a constant voltage to the MOStransistors and the resistors arranged in various circuits. To solvethis problem, elements such as MOS transistors and resistors are formedin test patterns, a voltage is applied to the test patterns, andcurrents flowing through the test patterns are measured. Then, theelectrical parameters of the MOS transistor and the resistors formed inthe actual semiconductor device are estimated. The test patterns areformed in regions that are defined between regions where thesemiconductor devices are formed.

FIG. 1 is a flowchart of a method for manufacturing a semiconductordevice.

Designed semiconductor devices are manufactured on a wafer in step S1.In step S2, electrical parameters of the manufactured semiconductordevices are monitored. This monitoring operation aims to inspect if MOStransistors and resistors formed in the semiconductor devices have thedesired electrical characteristics. In step S3, the functions of thesemiconductor devices are tested at the wafer level in order todetermine if the semiconductor devices operate normally. In step S4,only normal semiconductor devices are packaged. In step S5, the packagedsemiconductor devices are tested. In step S6, the semiconductor devicespassing the package test are put into the market.

FIG. 2 is a plan view of a wafer on which the semiconductor devices aremanufactured.

Several tens to several hundreds of semiconductor devices aremanufactured on a single wafer 10. A test circuit 20 is arranged betweenregions where the semiconductor devices are manufactured. The testcircuit 20 uses test patterns for testing if unit elements of thesemiconductor devices, such as MOS transistors and resistors, have thesame electrical characteristics as designed. The test patterns are notarranged to correspond to all semiconductor devices manufactured at thewafer level. The reason for this is that a space between thesemiconductor devices is insufficient.

The semiconductor devices are manufactured using a photo process, anetching process, and a deposition process. When these processes arefinished, one layer among multiple layers of the semiconductor device isformed. In order to form a next layer, the photo process, the etchingprocess and the deposition process are again performed. The photoprocess is not separately performed on the semiconductor devices, but itis performed on as many semiconductor devices as the number of photoshots supported by one photo equipment. For example, if one-time photoshot corresponds to four semiconductor devices, the same layers of foursemiconductor devices can be formed by the photo process. Since theregions formed by one-time photo process have the same characteristics,test patterns are arranged one by one in the regions where one-timephoto process is possible.

FIG. 3 is a circuit diagram of the test circuit 20 of FIG. 2.

The test circuit 20 includes a plurality of MOS transistors M1 to M6 andresistors RG and RM arranged in parallel. The MOS transistors M1 to M6have different channel lengths and widths in order to test the channellengths and widths of all MOS transistors. The resistor RG is a testpattern for measuring a gate resistance of the MOS transistor, and theresistor RM is a test pattern for measuring a line resistance.

Each of the MOS transistors M1 to M6 has one terminal connected to aground pad VSS PAD, and a gate commonly connected to a gate voltage padVG PAD. The MOS transistors M1 to M6 have the other terminals connectedto test pads VD1 PAD to VD8 PAD receiving corresponding test voltages,respectively. A method for testing the MOS transistors M1 to M6 includesthe steps of: applying a gate voltage to their gates; applyingcorresponding test voltages to first terminals of the MOS transistors M1to M6; and measuring currents flowing through the common pad VSS PAD.Whether the MOS transistors M1 to M6 are normally manufactured can beverified by checking the currents. Also, the resistors RG and RM can betested by measuring currents corresponding to a voltage differenceacross the resistors RG and RM.

When the semiconductor devices pass the test for the test circuit, itcan be concluded that the semiconductor devices formed on the wafer aremanufactured as designed. However, if the basic electricalcharacteristics of the semiconductor devices are analogized using onetest pattern, there can occur error in the electrical characteristics ofthe actual semiconductor devices. As the technology is developed, thesemiconductor devices are highly integrated, the circuit area occupiedby one semiconductor device is reduced. Thus, the number ofsemiconductor devices to be analogized using the test patternsincreases. Therefore, the electrical characteristics of the testpatterns become increasingly different from those of unit elements ofthe actual semiconductor devices.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a testcircuit that can test the electrical characteristics of thesemiconductor device more correctly.

In accordance with an aspect of the present invention, there is provideda semiconductor device including: a command control circuit for decodinga command signal to output a test signal and a normal control signal; anormal circuit for performing a predetermined operation in response tothe normal control signal; and a test circuit for testing electricalcharacteristics of unit elements provided in the normal circuit inresponse to the test signal.

In accordance with another aspect of the present invention, there isprovided a semiconductor device including: a normal circuit; a testsignal generator circuit for counting a clock signal to output aplurality of test signals; and a plurality of unit testers enabled inresponse to the test signals to test electrical characteristics of unitelements provided in the normal circuit.

In accordance with a further aspect of the present invention, there isprovided a test method of a semiconductor device having a normal circuitand a test circuit having a plurality of unit testers for testingelectrical characteristics of unit elements provided in the normalcircuit, the test method includes: generating a test clock signal;generating a plurality of test signals using the test clock signal; andoperating a corresponding one of the unit testers in response to acorresponding one of the test signals.

In accordance with the present invention, the test circuit for testingthe electrical parameters of the semiconductor device is provided withinthe semiconductor device. Thus, in testing the functions of thesemiconductor device, electrical characteristics of unit elements of thesemiconductor device can be tested at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the preferredembodiments given in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a flowchart illustrating a known method for manufacturing asemiconductor device;

FIG. 2 is a plan view of a wafer;

FIG. 3 is a circuit diagram of a test circuit of FIG. 2;

FIG. 4 is a block diagram of a semiconductor device in accordance withan embodiment of the present invention;

FIG. 5 is a block diagram of a test signal generator of FIG. 4;

FIG. 6 is a circuit diagram of a dividing unit illustrated in FIG. 5;

FIG. 7 is a waveform diagram illustrating an operation of the testsignal generator of FIG. 5;

FIG. 8 is a diagram illustrating an operation of the test signalgenerator of FIG. 5; and

FIG. 9 is a circuit diagram of an electrical parameter monitor of FIG.4.

DETAILED DESCRIPTION OF THE INVENTION

A semiconductor device in accordance with exemplary embodiments of thepresent invention will be described in detail with reference to theaccompanying drawings.

FIG. 4 is a block diagram of a semiconductor device in accordance withan embodiment of the present invention.

The semiconductor device includes a command control circuit 1000, anormal circuit 2000, and a test circuit 3000. The command controlcircuit 1000 decodes an external command CMD to output a test signal TMand a normal control signal ICMD. The normal circuit 2000 performs apredetermined operation in response to the normal control signal ICMD.The test circuit 3000 tests electrical characteristics of unit elementsof the normal circuit 2000 in response to the test signal TM.

The normal circuit 2000 represents all circuits for performingoperations of the semiconductor device. The test circuit 3000 performs atest operation using test patterns in response to the test signal TMthat is constantly clocked.

The test circuit for testing the electrical parameters is includedwithin the semiconductor device. Thus, in testing the functions of thesemiconductor device, electrical characteristics of unit elements of thenormal circuit 2000, such as MOS transistors and resistors, can also betested.

More specifically, the test circuit 3000 includes a test signalgenerator 100 and an electrical parameter monitor 200. The test signalgenerator 100 counts the test signal TM to output a plurality of testcontrol signals TMC<1:i>. The electrical parameter monitor 200 includesa plurality of unit testers for testing electrical characteristics ofunit elements of the normal circuit 2000 in response to the test controlsignals TMC<0:i>.

The test circuit 3000 further includes a control signal input pad 300, acommon test signal input pad 400, and a common test pad 500. The controlsignal input pad 300 is configured to receive a control signal forcontrolling and enabling of the unit testers. The common test signalinput pad 400 is configured to provide test input signals to the unittesters of the electrical parameter monitor 200. The common test pad 500is configured to receive test output signals from the unit testers.

FIG. 5 is a block diagram of the test signal generator of FIG. 4.

The test signal generator 100 includes a first dividing unit 110 fordividing the test signal TM in a first division ratio, a second dividingunit 120 for dividing an output signal CNT<0> of the first dividing unit110 in a second division ratio, a third dividing unit 130 for dividingan output signal CNT<1> of the second dividing unit 120 in a thirddivision ratio, a fourth dividing unit 140 for dividing an output signalCNT<2> of the third dividing unit 130 in a fourth division ratio, and adecoding unit 150 for decoding the output signals CNT<0> to CNT<3> ofthe first to fourth dividing units 110, 120, 130 and 140 to output thetest control signals TMC<1> to TMC<15>. The first to fourth divisionratios may be equal to or different from one another. The first tofourth division ratios can be appropriately determined according tointernal circuits of the decoding unit 150 and the dividing units.

The decoding unit 150 includes a plurality of AND gates ND1 to ND16 forANDing the output signals CNT<0> to CNT<3> of the first to fourthdividing units 110 to 140. The AND gates ND1 to ND16 are configured toreceive signals having a different logic combination.

FIG. 6 is a circuit diagram of the first dividing unit 110 of FIG. 5.Since the second to fourth dividing units 120, 130 and 140 have the samestructure as that of the first dividing unit 110, their detaileddescription will be omitted.

The first dividing unit 110 includes first and second latches LAT1 andLAT2, a transmission gate T1, a first inverter I1, and a firstthree-phase inverter I2, and counts the test signal TM to output thedivided-by-2 signal CNT<0>. The first latch LAT1 includes a secondthree-phase inverter 13 and a NAND gate ND, and the second latch LAT2includes second and third inverters 14 and 15. A reset control signalRSTB is inputted to the NAND gate ND.

FIG. 7 is a waveform diagram illustrating an operation of the testsignal generator 100 of FIG. 5.

The first dividing unit 110 of the test signal generator 100 divides thetest signal TM by 2 to output the signal CNT<0>. The second dividingunit 120 divides the output signal CNT<0> of the first dividing unit 110by 2 to output the signal CNT<1>. The third dividing unit 130 dividesthe output signal CNT<1> of the second dividing unit 120 by 2 to outputthe signal CNT<2>. The fourth dividing unit 140 divides the outputsignal CNT<2> of the third dividing unit 130 by 2 to output the signalCNT<3>. The decoding unit 150 selectively outputs 16 decoding testcontrol signals TMC<1:15> using the output signals CNT<0> to CNT<4> ofthe dividing units 110 to 140.

FIG. 8 is a diagram illustrating an operation of the test signalgenerator 100 of FIG. 5.

The states in which the decoder 150 outputs the 16 decoded test controlsignals TMC<1:15> using the output signals CNT<0> to CNT<3> of thedividing units 110 to 140 can be seen from FIG. 8. As illustrated inFIG. 7, the test control signals TMC<1:15> can be efficiently generatedusing one test signal TM. Also, in testing the function of thesemiconductor device, the test circuit 1000 is also operated. Thus, theelectrical parameters of the unit elements of the semiconductor devicecan be tested at the same time.

FIG. 9 is a circuit diagram of the electrical parameter monitor of FIG.4.

The electrical parameter monitor 200 includes a plurality of unittesters 210 to 280. Each of the unit testers 210 to 280 includes thesame types of unit elements as those of the normal circuit 2000, such asMOS transistors and resistors.

For example, the first unit tester 210 includes a first test MOStransistor M7 and a first switching MOS transistor P1. The first testMOS transistor M7 has one terminal receiving the test input signalthrough the test signal input pad 400, and a gate receiving the controlsignal through the control signal input pad 300. The first switchingPMOS transistor P1 has one terminal connected to the other terminal ofthe first test MOS transistor M7, a gate receiving the test controlsignal, and the other terminal connected to Vss. The control signalinput through the control signal input pad 300 is a signal to provide avoltage for turning on the first test MOS transistor M7. A channellength and width of the first test MOS transistor M7 in the first unittester 210 are equal to those of a MOS transistor of the normal circuit.

The control signal input through the control signal input pad 300 may beprovided by a separate circuit. Also, a reference signal used in aninput circuit receiving an input signal during a normal operation may beused as the control signal. In order to receive the signal at a highspeed, the input circuit is configured to receive differential signals.One of the differential signals is an external signal, and the other isan internal reference signal. In this case, the reference signal may beused as a signal that is provided to the control signal input pad.

A seventh unit tester 270 includes a test resistor RG2 and a seventhswitching MOS transistor P7. The test resistor RG2 has one terminalreceiving the test input signal through the test signal input pad 400.The seventh switching MOS transistor P7 has one terminal connected tothe other terminal of the test resistor RG2, a gate receiving the testcontrol signal, and the other terminal connected to the test pad 500.The test resistor RG2 is designed to have the same resistance as that ofthe resistor of the normal circuit 2000.

As described above, the unit testers of the electrical parameter monitor200 correspond to various kinds of MOS transistors and resistors of thenormal circuit 2000, and are designed to be equal to the unit elements.

In order to test the electrical characteristic of the first test MOStransistor M7, the first test MOS transistor M7 is turned on byinputting the control signal to its gate when the test control signalTMC<1> from the test signal generator 100 becomes a high level. The testvoltage is applied through the test signal input pad 400, and an amountof current flowing through the test pad 500 is measured. In this way, itis possible to verify whether the first test MOS transistor M7 isnormal. Since the first test MOS transistor M7 is provided within thesemiconductor device, it can be determined that all MOS transistorscorresponding to the first test MOS transistor M7 operate normally ifthe MOS transistor M7 operates normally. Like the resistors of theseventh and eighth unit testers 270 and 280 are equally applied.

As described above, since the test circuits are provided within thesemiconductor device, the electrical characteristics of the unitelements of the manufactured semiconductor device can be tested morecorrectly.

Since the test patterns for testing the electrical characteristics ofthe unit elements of the semiconductor device are provided within thesemiconductor device, the electrical characteristics of the unitelements can be tested more correctly. Moreover, in testing thefunctions of the semiconductor device, the electrical characteristicscan also be tested. Thus, the characteristics of the semiconductordevice can be tuned according to the electrical characteristics.Consequently, the characteristics of the manufactured semiconductordevice can be enhanced.

The present application contains subject matter related to Korean patentapplication No. 2006-83532, filed in the Korean Intellectual PropertyOffice on Aug. 31, 2006, the entire contents of which are incorporatedherein by reference.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

1. A semiconductor device, comprising: a test signal generator configured to generate a plurality of test signals; a plurality of first unit elements configured to be corresponding to a plurality of second unit elements arranged in a normal circuit; and a plurality of unit testers configured to selectively test electrical characteristics of the plurality of first unit elements to output a plurality of test control signals in response to the plurality of test signals, respectively, wherein the test signal generator includes: a plurality of dividing units for dividing the test signal in different division ratios; and a decoding unit for decoding the output signals of the plurality of dividing units to output the test control signals.
 2. The semiconductor device of claim 1, wherein the plurality of first unit elements include a plurality of MOS transistors and resistors.
 3. The semiconductor device of claim 2, wherein the characteristics of the MOS transistors are equal to the characteristics of MOS transistors provided in the normal circuit.
 4. The semiconductor device of claim 1, wherein the characteristics of each of the plurality of first elements are same with the characteristics of each of the plurality of second elements in the normal circuit.
 5. The semiconductor device of claim 1, further comprising: a common test signal input pad configured to provide test input signals to the plurality of unit testers; and a control signal input pad configured to input a control signal for controlling an enabling of the unit testers.
 6. The semiconductor device of claim 5, wherein the plurality of unit testers include: a test MOS transistor having one terminal receiving the test input signal through the common test signal input pad, and a gate receiving the control signal through the control signal input pad; and a switching MOS transistor having one terminal connected to the other terminal of the test MOS transistor, a gate receiving the test control signal, and the other terminal connected to the test pad.
 7. The semiconductor device of claim 1, wherein each of the plurality of dividing units includes: a first dividing unit for dividing the test signal in a first division ratio; and a second dividing unit for dividing an output signal of the first dividing unit in a second division ratio.
 8. The semiconductor device of claim 7, wherein the decoding unit decodes the output signal of the first dividing unit and the output signal of the second dividing unit to output the test control signals.
 9. The semiconductor device of claim 7, wherein the decoding unit includes a logic gate for performing an AND operation to the output signal of the first dividing unit and the output signal of the second dividing unit. 